Surface coatings, treatments, and methods for removal of mineral scale by self-release

ABSTRACT

In some aspects, the present invention relates generally to self-release compositions and methods useful for the removal or prevention of mineral scaling and, more particularly, to surface coatings and surface treatments that resist, prevent, or aid in removal of mineral scaling. In some aspects, the self-release coating includes a polyhedral oligomeric silsesquioxane and a thermoplastic or an additive.

CROSS-REFERENCES TO RELATED APPLICATION

This application is a divisional of pending U.S. application Ser. No.15/675,070 (filed Aug. 11, 2017), which was a continuation of U.S.application Ser. No. 14/732,652 (filed Jun. 5, 2015), which claimedpriority to and benefit of U.S. Provisional Application No. 62/008,828(filed Jun. 6, 2014). These applications are related to InternationalApplication No. PCT/US15/34407 (filed Jun. 5, 2015). The entire contentsof each of these applications are hereby incorporated by reference.

RIGHTS OF THE GOVERNMENT

The invention described herein may be manufactured and used by or forthe Government of the United States for all governmental purposeswithout the payment of any royalty.

FIELD OF THE INVENTION

In some aspects, the present invention relates generally to the removalor prevention of mineral scaling and, more particularly, to surfacecoatings and surface treatments that resist, prevent, or aid in removalof mineral scaling.

BACKGROUND OF THE INVENTION

Mineral fouling is a common occurrence in a variety of residential,commercial, and industrial operations when substrates are exposed tonaturally occurring or so-called “tap” water. Some of the morerecognizable examples include residential water heaters, residentialshower heads, commercial HVAC systems having cooling towers or heatexchangers, heat exchangers in the chemical process industry, and oiland gas extraction operations. Mineral fouling, or the formation ofmineral scale, is a result of the precipitation of salts dissolved inthe water onto the substrate. Mineral scale can take the form of anaccumulation of relatively soft deposits, generally caused by thedeposition of minerals that precipitate in the bulk fluid. Soft scale istypically easy to remove. However, the solubility of dissolved saltsdecreases with temperature. Therefore, when the surface of a heatedsubstrate is exposed to water containing dissolved salts, salts candirectly precipitate onto the surface. Such directly precipitateddeposits, which often comprise a combination of many different mineralsincluding calcium sulfate and calcium carbonate, are extremely durableand resist removal via mechanical abrasion and/or dissolution by acids.As deposits accumulate on equipment surfaces, such as heat exchangers,the resistance to heat transfer increases, which results in decreasedenergy efficiency. It has been estimated that up to 0.25% of grossdomestic product value is lost because of the inefficiencies in processequipment introduced by mineral scaling.

Numerous technologies have been developed to resist mineral scaling.Most of these conventional technologies rely on additives, introducedinto the processing of water, to inhibit precipitation. However, theseadditives must be constantly supplied and replenished and may constitutecontaminants in wastewater streams requiring expensive post-treatmentprocesses to mitigate environmental concerns. More sophisticatedtechniques to reduce scaling include electromagnetic devices that exposea portion of the process water to a large magnetic field. The magneticfield is designed to disturb the motion of ions in the process waterand, thereby, promote precipitation. By precipitating salts away fromcritical process equipment, the amount of subsequent precipitation toform mineral scale on critical equipment surfaces can be reduced. Suchelectromagnetic devices require a continuous power supply, are expensiveto fabricate and maintain, and require additional space forinstallation, operation, and maintenance.

Yet another conventional, more elegant solution to mineral scaling isdevelopment of surface treatments or coatings that discourage oreliminate the growth of scale. As used herein, a “treatment” meansapplication of a chemical compound to the surface of a substrate so asto form a deposit thereon that is not a mechanically-distinct layeroverlying the surface and cannot exhibit layer behavior, such asdelamination or peeling. As used herein, a “coating” means deposition ofa chemical compound to the surface of a substrate so as to form amechanically discrete layer that exhibits layer behavior, such as, acapacity of being peeled off. In the absence of information aboutmechanical properties, a layer having a thickness of less than about 10nm will be considered a “treatment” while a layer having a thicknessgreater than about 10 nm will be considered a “coating.” Conventionaltreatments and/or coatings that inhibit the growth of mineral scaleinclude hydrophobic coatings, such as DuPont's Teflon® coatings, orhydrophilic coatings. In systems using mixtures of oil and water as aprocess fluid, the coatings that wet oil and that do not absorb waterare preferred for resisting the growth of mineral scale. One suchconventional coating includes an oil that is immiscible with water andprevents contact with the aqueous phase comprising the dissolvedminerals. Still other conventional solutions include manufacture ofsurfaces having an energy of formation per unit area of less than about32 mJ/m² and/or a ratio of polar-to-total energy of formation of lessthan 0.2. Such surfaces resist the accumulation of mineral scale instatic environments due to a presumed decrease in the nucleation ofmineral salt crystals on the surface of a substrate (e.g., microscopeslides).

These conventional treatments and/or coatings are limited to resistingan initiation of mineral scale growth. If a material scale depositbegins, such as at a defect in the coating or treatment, then resistanceto further accumulation of material scale is lost. Therefore, theseconventional treatments or coatings lack the continuous counteractionprovided by chemical or electromagnetic water treatment methods,described previously. Because the coatings on materials used inresidential, commercial, and industrial environments (as opposed tolaboratory environments) are likely to include defects, the practicalvalue of coatings and/or treatments may be limited.

Despite these various advancements in the field of mineral scaling,there remains a need for improved methods by which the accumulation ofmineral scale can be resisted. It would be desirable for such improvedmethods to combine the elegance of a simple surface treatment or coatingwith the continuous counteraction provided by chemical orelectromagnetic water treatments and that may be realized by applicationof a thin-layer treatment or coating without a substantial increase inthermal resistance (generally speaking, the thermal resistance isproportional to a layer thickness divided by a thermal conductivity).

Fundamental studies of the adhesion of solid objects to polymericcoatings, such as the ice adhesion study of Meuler et al., ACS Appl.Mater. Interfaces, Vol. 2, pp. 3100-3110 (“Meuler”) have shown that,when very thin coatings on rigid substrates are used, the “practicalwork of adhesion” decreases as the receding contact angle of the surfacein contact with an appropriate probe liquid increases. The force neededto remove a solid object from such a surface is proportional to thepractical work of adhesion. As a result, the receding contact anglemeasured using an appropriate probe liquid provides a reliableindication of the relative amount of force (per unit area) needed toremove a solid object from the surface. For the adhesion of ice, liquidwater is clearly the most appropriate probe liquid. For othersubstances, however, such as adhered metal, the use of a molten form ofthe solid as a probe liquid is not practical, as it may requiretemperatures that would destroy the coating.

Moreover, it is well known to those skilled in the art of adheringsurfaces that the roughness of a surface is a critical determinant ofadhesion. Smooth surfaces are known to have significantly lower adhesionthan rough surfaces. Generally speaking, a rougher surface provides agreater true surface area than a smooth surface, thus increasing thetotal force required to remove an object from said surface even when the“work of adhesion,” which is the energy required per unit of truesurface area, remains the same. Furthermore, roughening of surfacesprovides locations where mechanical interlocking of the surface and anadhered object may occur. Removal of the solid object then requiresovercoming the mechanical interlocking forces in addition to overcomingthe work of adhesion. Conveniently, the receding contact angle of afully wetted surface is known to decrease with increasing roughness.Thus, as an indicator of adhesion, the receding contact anglemeasurement accounts not only for chemical interactions betweensurfaces, but also for roughness.

In addition to roughness, the physical and chemical heterogeneity of asurface also contribute to the adhesion of solid objects. In particular,heterogeneous surfaces contain locations of increased affinity betweenthe surface and an adhered solid object, due either to chemical speciesor to physical topography that “pins” an adhered object to the surface.These heterogeneities may be considered as “pinning defects.” Thegreater the number and tenacity of these pinning defects, the greaterthe adhesion of a solid object to a surface will be. Again,conveniently, the presence of pinning defects tends to increase thedifference between advancing and receding contact angles on a surface.Because the receding contact angle is, in all but exceptionally rarecases, smaller than the advancing contact angle, the presence of pinningdefects will decrease the receding contact angle as it increases thedifference between the advancing and receding angle. Therefore, thereceding contact angle also captures effects due to pinning defects onsurface adhesion.

Beyond the aforementioned effects, it is also possible for the molecularfragments present on many surfaces to reorganize into new physicalarrangements upon contact with liquids and solids. Such rearrangementsalmost always draw molecular fragments with an affinity for the adheringsubstance closer to the surfaces, but push away fragments with a loweraffinity. Such rearrangements therefore increase the adhesion of solidand liquid objects to surfaces. Again, conveniently, this phenomenonleads to a difference between advancing and receding contact angles asmeasured on a surface. As described before, the net result is thatsurfaces with a greater capacity to reorganize in contact with aparticular liquid will demonstrate a lower receding contact angle. As anindicator of adhesion, therefore, receding contact angles also captureeffects due to surface reorganization.

Surfaces having a terminal —CF₃ molecular fragment at the outermostmolecular layer are known to have generally the highest contact angleswith water, the lowest surface energies, and the lowest levels ofadhesion and frictional interaction with solids and liquids. When these—CF₃ fragments are immediately adjacent to fragments other than —CF₂—linking fragments, dipolar forces result that increase adhesion.Moreover, surfaces with —CF₃ fragments connected to a small number of,or no, adjacent —CF₂— linking fragments are prone to reorganization. Itis therefore known that, to produce a surface having minimal adhesion tosolid or liquid objects, a well-ordered array of —CF₃ fragments adjacentto as many —CF₂-linking fragments as possible, having minimal roughnessand minimal defects, is required. Although methods of chemicalmodification, for instance with silanes, are known to produce suchsurfaces, at present, general methods and compositions for producingsuch surfaces using discrete molecules, without chemical modification ofan underlying substrate, are not known. Such methods and compositionsmust satisfy the following requirements: 1) allow for self-assembly of awell-ordered monolayer of —CF₃ fragments adjacent to numerous—CF₂-linking fragments within a practical time frame, 2) maintain thisarrangement under conditions of operation for a long enough period to beof practical use, 3) prohibit naturally occurring surface rearrangements(such as the growth of large crystalline domains) that produce pinningdefects, and 4) produce surfaces with the minimum possible roughness.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes the foregoing problems and othershortcomings, drawbacks, and challenges of resisting and/or removingaccumulations of mineral scale. While the invention will be described inconnection with certain embodiments, it will be understood that theinvention is not limited to these embodiments. To the contrary, thisinvention includes all alternatives, modifications, and equivalents asmay be included within the spirit and scope of the present invention.

In one aspect, the present invention sets forth a self-releasecomposition that includes a polyhedral oligomeric silsesquioxane and athermoplastic, wherein the polyhedral oligomeric silsesquioxane is a—CF₃ terminal fluorous compound.

In one aspect, the present invention sets forth a self-releasecomposition including a polyhedral oligomeric silsesquioxane and anadditive, wherein the additive imparts a surface energy of less thanabout 15 mJ/m²; and wherein at least one member of the group consistingof the polyhedral oligomeric silsesquioxane and the additive is a —CF₃terminal fluorous compound.

In one aspect, the present invention sets forth a method of removing amineral scale from the substrate comprising a self-release compositioncoating as otherwise described herein, the method including directing aturbulent flow toward an interface between the mineral scale and thesubstrate surface.

In one aspect, the present invention sets forth a method of preparing aself-release substrate as otherwise described herein, the methodincluding:

combining a —CF₃ terminal fluorous polyhedral oligomeric silsesquioxanewith a thermoplastic to make a mixture;

applying the mixture to a substrate surface; and

drying the applied mixture on the substrate surface.

In one aspect, the present invention sets forth a method of preparing aself-release substrate, the method including:

applying at least two layers that include a —CF₃ terminal fluorouspolyhedral oligomeric silsesquioxane to a substrate surface to form afirst plurality of —CF₃ terminal fluorous oligomeric silsesquioxanelayers;

applying a layer comprising at least two layers that include athermoplastic to the substrate surface to form a second plurality ofthermoplastic layers; and

drying the applied layers on the substrate surface.

In one aspect, the present invention sets forth a method of preparing aself-release substrate, the method including:

applying at least two layers that include an additive to a substratesurface to form a first plurality of additive layers, wherein theadditive imparts a surface energy of less than about 15 mJ/m², andwherein the additive is a —CF₃ terminal fluorous compound;

applying at least two layers that include a thermoplastic to thesubstrate surface to form a second plurality of thermoplastic layers;and

drying the applied layers on the substrate surface.

Additional objects, advantages, and novel features of the invention willbe set forth in the description that follows and will also becomeapparent to those skilled in the art upon examination of the followingor may be learned by practice of the invention. The objects andadvantages of the invention may be realized and attained by means of theinstrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the presentinvention and, together with a general description of the inventiongiven above, and the detailed description of the embodiments givenbelow, serve to explain the principles of the present invention.

FIG. 1 is a flowchart illustrating a method of preparing and applying asurface coating to a substrate in accordance with an embodiment of thepresent invention.

FIG. 2 is a schematic, line-drawing representation of a chemicalstructure of a fluorinated polyhedral oligomeric silsesquioxaneaccording to an embodiment of the present invention.

FIGS. 3A to 3C are a sequential, schematic representation of a method ofremoving mineral scale from a substrate having the surface coating ofFIG. 1 and in accordance with an embodiment of the present invention.

FIG. 4 is an apparatus used to test the self-release properties ofpipes, as is discussed in Example 1.

FIG. 5 is a side-elevational view of a substrate having an adhesive tapeapplied thereto for adhesion testing in accordance with the exemplarytesting procedures.

FIG. 6 is a photograph of a stainless steel tube treated or coated witha mixture of F-decyl POSS and poly(methyl methacrylate), i.e., the“blue” or B tube of Example 2, during operation of a test heat exchangerand showing self-release of mineral scale.

FIG. 7 is a photograph of a stainless steel tube treated with a controltest composition containing Asahiklin AK225G, i.e., the “white” or Wtube of Example 2, during operation of a test heat exchanger and,showing little-to-no self-release of mineral scale.

FIG. 8 is a photograph of three stainless steel tubes: the red tube(top, “R”), the blue tube (middle, “B”), and the white tube (bottom,“W”), prepared in accordance with Example 2, after the tubes are removedfrom a test heat exchanger.

FIGS. 9A and 9B are a set of comparative surface topographic maps inwhich a spin-coated mixture of octakis(1H,1H,2H,2H-heptadecafluorodecyl) silsesquioxane, and poly(methylmethacrylate), deposited from Asahiklin AK225G solvent, is shown beforeand after heat treatment at 90° C. for 1 hour.

FIG. 10 is a plot of advancing and receding contact angles fordip-coated surfaces containing a mixture of octakis(1H,1H,2H,2H-heptadecafluorodecyl) silsesquioxane, and poly(methylmethacrylate), deposited from Asahiklin AK225G solvent, as a function ofsurface roughness.

FIG. 11 shows an example photograph of four stainless steel tubes: thered tube (top, “R”), white tube (second from top, “W”), the blue tube(second from bottom, “B”), and the green tube (bottom, “G”). Regions oflocalized, high shear forces have caused self-release of mineral foulingfrom surfaces containing a mixture of octakis(1H,1H,2H,2H-heptadecafluorodecyl) silsesquioxane, and poly(methylmethacrylate), deposited from Asahiklin AK225G solvent, but noself-release in the same location from a control surface containingneither the silsesquioxane nor the poly(methyl methacrylate).

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the sequence of operations as disclosedherein, including, for example, specific dimensions, orientations,locations, and shapes of various illustrated components, will bedetermined in part by the particular intended application and useenvironment. Certain features of the illustrated embodiments have beenenlarged or distorted relative to others to facilitate visualization andclear understanding. In particular, thin features may be thickened, forexample, for clarity or illustration.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described herein. In addition, the materials, methods, andexamples described are illustrative only and not intended to belimiting. All publications, patent applications, patents, and otherreferences mentioned herein are incorporated by reference in theirentirety. In case of conflict, the present specification, includingthese definitions, will control.

The terms “a,” “an,” or “the” as used herein not only include aspectswith one member, but also include aspects with more than one member. Forexample, an aspect including “an additive and a thermoplastic” should beunderstood to present certain embodiments with at least a secondadditive, at least a second thermoplastic, or both.

The term “about” as used herein to modify a numerical value indicates adefined range around that value. If “X” were the value, “about X” wouldgenerally indicate a value from 0.95X to 1.05X. Any reference to “aboutX” specifically indicates at least the values X, 0.95X, 0.96X, 0.97X,0.98X, 0.99X, 1.01X, 1.02X, 1.03X, 1.04X, and 1.05X. Thus, “about X” isintended to teach and provide written description support for a claimlimitation of, e.g., “0.98X.” When the quantity “X” only includeswhole-integer values (e.g., “X carbons”), “about X” indicates from (X−1)to (X+1). In this case, “about X” as used herein specifically indicatesat least the values X, X−1, and X+1.

When the term “about” is applied to the beginning of a numerical range,it applies to both ends of the range. Thus, “from about 5 to 20%” isequivalent to “from about 5% to about 20%.” When “about” is applied tothe first value of a set of values, it applies to all values in thatset. Thus, “about 7, 9, or 11%” is equivalent to “about 7%, about 9%, orabout 11%.” However, when the modifier “about” is applied to describeonly the end of a range or only a later value in a set of values, itapplies only to that value or that end of the range. Thus, the range“about 2 to 10” is the same as “about 2 to about 10,” but the range “2to about 10” is not.

In compositions comprising an “additional,” “further,” or “second”component or step, the “second” component or step is chemicallydifferent from the first component. A “third” component is differentfrom the other, first, and second components, and additional enumeratedor “further” components or steps are similarly different.

The terms “adhesion” and “adhesive strength” as used herein refers to anintrinsic property of an arrangement of molecules at a surface and theforce required to detach them from the surface. The adhesion andadhesive strength may be defined for a region of any size down to thescale of individual molecules, and may vary from location to location atthe surface, whereas the self-release characteristic is a binary(present or not present) feature of the surface.

The term “alkyl” as used herein includes an aliphatic hydrocarbon chainthat may be straight chain or branched. The aliphatic hydrocarbon chainmay contain an indicated number of carbon atoms: For example, C₁-C₁₂indicates that the group may have from 1 to 12 (inclusive) carbon atomsin it. If not otherwise indicated, an alkyl group may include about 1 toabout 20 carbon atoms. In one aspect, alkyl groups have 1 to about 12carbon atoms in the chain. In another aspect, alkyl groups (“loweralkyl”) have 1 to about 6 carbon atoms in the chain. Examples mayinclude, but are not limited to, methyl; ethyl; propyl; isopropyl (iPr);1-butyl; 2-butyl; isobutyl (iBu); tert-butyl; pentyl; 2-methylbutyl;1,1-dimethylpropyl; hexyl; heptyl; octyl; nonyl; decyl; docecyl;cyclopentyl; or cyclohexyl.

The linking term “comprising” or “comprise” as used herein is notclosed. For example, “a composition comprising A” must include at leastthe component A, but it may also include one or more other components(e.g., B; B and C; B, C, and D; and the like).

As used herein, a “fluorous” or “fluorinated” group is a group thatincludes one or more fluoro-substituents. Examples include, but are notlimited to, trifluoromethyl and perfluorobutyl. In one aspect (i.e., a“—CF₃ terminal fluorous” group), the fluorous group comprises at leastone terminal trifluoromethyl group (i.e., a “—CF₃ terminal fluorous”group as otherwise set forth herein). In one aspect, a fluorous groupincludes a polyfluorinated subgroup, which may be adjacent to the —CF₃groups to create a polyfluorinated subdomain. For example, the group—(CH₂)_(n)(CF₂)_(m)CF₃, in which n is an integer from 1 to 10 and m isan integer from 4 to 9, is one embodiment of a —CF₃ terminal fluorousgroup.

As used herein, the term “or” should in general be construednon-exclusionarily. For example, “a composition comprising A or B” wouldalso apply to an embodiment comprising both A and B. “Or” should,however, be construed to exclude those aspects presented that cannot becombined without contradiction (e.g., a thickness of 10 to 40 nm and athickness of 100 to 200 nm).

The terms “self-release” or “self-release” as used herein are directedto an aspect of a surface immersed (at least partially) in a fluidmedium. The term “self-release” indicates that an adhered material(e.g., a solid, such as a mineral scale) will detach from one or morelocations on the surface due only to mechanical forces generated by theimmersing fluid, such as the force from fluid flow along theself-release surface. In particular, the term “self-release”indicatesthat no external mechanical action by other solid objects, such asscrubbing, scraping, rubbing, abrading, or grinding, is required todetach an adhered material from the self-release surface. In oneembodiment of the present invention, the adhered material is an area ofmineral scale produced by exposure to hard water.

In the present invention, the flow characteristics of the fluid are notarbitrary, but are limited to those encountered in common industrialprocesses, such as heat exchange and interior flow within a pipeline.Supersonic fluid flows or flows of plasma jets are excluded. Flowingfluid that exclusively takes the form of sprayed jets or another form inwhich sprayed droplets of the fluid impart forces primarily throughelastic collisions with the surface is also excluded.

The term “self-release” is distinct from terms such as “low adhesion” inthat “self-release” is a performance characteristic of an extended solidobject that depends on the surface topography, adhesive characteristics,and the uniformity of those characteristics across an extended area. Acoating is described as a self-release coating if the surface formed byapplying the coating to an object exhibits the characteristic of selfrelease.

The terms “weight percent,” “w/w,” and “wt/wt” as used herein refer to apercentage expressed in terms of the weight of the ingredient or agentover the total weight of the composition multiplied by 100.

In one aspect, the present invention sets forth a self-releasecomposition that includes a polyhedral oligomeric silsesquioxane and athermoplastic. In a more specific aspect, the polyhedral oligomericsilsesquioxane is a —CF₃ terminal fluorous compound.

In one aspect, the present invention sets forth a self-releasecomposition including a polyhedral oligomeric silsesquioxane and anadditive, wherein the additive imparts a surface energy of less thanabout 15 mJ/m². In a more specific aspect, at least one member of thegroup consisting of the polyhedral oligomeric silsesquioxane and theadditive is a —CF₃ terminal fluorous compound.

In one aspect, the present invention sets forth a self-releasecomposition as set forth elsewhere herein, further including a solvent.In a more specific aspect, the solvent is a semi-fluorinatedhydrocarbon. In a still more specific aspect, the solvent includes3,3-dichloro-1,1,1,2,2-pentafluoropropane and1,3-dichloro-1,1,2,2,3-pentafluoropropane (e.g., Asahiklin AK225G orother commercially available semi-fluorinated hydrocarbons). Examples ofother commercially available semi-fluorinated hydrocarbons usable inthis aspect include 1,1,1,2,2,3,4,5,5,5-decafluoropentane;1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether; and1,1,2,2,3,3,4-heptafluorocyclopentane.

In one aspect, the present invention sets forth a self-releasecomposition as set forth elsewhere herein, wherein the compositionincludes from about 0.1% to about 70% (w/w) of the polyhedral oligomericsilsesquioxane. In a more specific aspect, the composition includes fromabout 0.25, 0.5, 0.75, 1, 2, 3, 4, 5, 6, 7, 8, or 9% (w/w) to about 31,32, 33, 34, 35, 36, 37, 38, 39, 40, 45, 50, 65, or 70% (w/w).

In a more specific aspect, the composition includes from about 10% toabout 30% (w/w) of the polyhedral oligomeric silsesquioxane. In a stillmore specific aspect, the composition includes about 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30% (w/w)of the polyhedral oligomeric silsesquioxane.

In one aspect, the present invention sets forth a self-releasecomposition as set forth elsewhere herein, wherein the compositionincludes from about 30% to about 99.99% (w/w) of the thermoplastic. In amore specific aspect, the composition includes from about 35, 40, 45,50, 55, 60, 61, 62, 63, 64, 65, 66, 67, 68, or 69% (w/w) to about 90,91, 92, 93, 94, 95, 96, 97, 98, 99, or 99.9% (w/w).

In a more specific aspect, the composition includes from about 70% toabout 90% (w/w) of the thermoplastic. In a still more specific aspect,the present invention sets forth a self-release composition as set forthelsewhere herein, wherein the composition includes about 70, 71, 72, 73,74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, or 90%(w/w) of the thermoplastic.

In one aspect, the present invention sets forth a self-releasecomposition as set forth elsewhere herein, wherein the polyhedraloligomeric silsesquioxane is a fluorous polyhedral oligomericsilsesquioxane. In a more specific aspect, the fluorous polyhedraloligomeric silsesquioxane is a —CF₃ terminal fluorous polyhedraloligomeric silsesquioxane. In one embodiment, the polyhedral oligomericsilsesquioxane is octakis(1H,1H,2H,2H-heptadecafluorodecyl) polyhedraloligomeric silsesquioxane.

In one aspect, the present invention sets forth a self-releasecomposition as set forth elsewhere herein, wherein the thermoplastic isa member selected from the group of poly(methyl methacrylate), amorphouspolyacrylate, poly(alkyl)acrylate, polystyrene, polyacrylonitrile,polysulfone, polyethersulfone, and poly-D-lactic acid. In oneembodiment, the thermoplastic is poly(methyl methacrylate).

In one aspect, the present invention sets forth a self-releasecomposition as set forth elsewhere herein, wherein the thermoplastic isan amorphous thermoplastic that is not swelled more than about 10% bywater, wherein the amorphous thermoplastic includes at most about 20%(w/w) fluorine, and wherein the amorphous thermoplastic includes about5% (w/w) of hydrophilic groups.

In one aspect, the present invention sets forth a self-releasecomposition as set forth elsewhere herein, further including anadditive, wherein the additive imparts a surface energy of less thanabout 15 mJ/m². In a more specific aspect, the additive is a —CF₃terminal fluorous compound. In one embodiment, the additive isperfluorooctanoic acid. In one embodiment, the additive is selected fromthe group consisting of perfluorooctanoic acid, perfluorohexanoic acid,perfluorooctane, and 1H,1H, 1H,2H,2H-heptadecafluorodecane.

In one aspect, the present invention sets forth a substrate, wherein thesubstrate has a substrate surface, and wherein a self-releasecomposition as otherwise described herein is applied to the substratesurface. In a more specific aspect, the self-release composition adheresto the substrate surface as a self-release coating.

In one aspect, the present invention sets forth a self-release coatingas otherwise described herein, wherein the self-release coating has athickness ranging from about 100 to 350 nm. In one aspect, theself-release coating has a thickness ranging from about 100 to 200 nm.In one aspect, the self-release coating has a thickness ranging fromabout 50 to 200 nm. In one aspect, the self-release coating has athickness ranging from about 25 to 150 nm. In one aspect, theself-release coating has a thickness ranging from about 10 to 100 nm. Inone aspect, the self-release coating has a thickness ranging from about10 to 50 nm.

In one aspect, the self-release coating has a thickness of about 500,450, 400, 350, 300, 275, 250, 225, or 200 nm. In one aspect, theself-release coating has a thickness of about 200, 175. 150, 125, 100,90, 80, 75, 70, 65, 60, 55, or 50 nm. In one aspect, the self-releasecoating has a thickness of about 50, 45, 40, 35, 30, 25, or 20 nm. Inone aspect, the self-release coating has a thickness of about 19, 18,17, 16, 15, 14, 13, 12, 11, or 10 nm.

In one aspect, the self-release surface is a self-release treatment witha thickness of about 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 nm.

In one aspect, the present invention sets forth a self-release coatingas otherwise described herein, wherein the self-release coating has aroughness of less than about 1000, 900, 800, 750, 700, 600, 500, 450,400, 350, 300, or 250 nm (e.g., from <1 to 250 nm). In one aspect, theself-release coating has a roughness of less than about 250, 225, 200,175, 150, 125, or 100 nm. In one aspect, the self-release coating has aroughness of less than about 100, 90, 80, 70, 60, 50, 45, 40, 35, 30,25, 20, 15, or 10 nm. In one aspect, the self-release coating has aroughness of less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 nm.

In one aspect, the present invention sets forth a method of removing amineral scale from the substrate as otherwise described herein, themethod including: directing a turbulent flow toward an interface betweenthe mineral scale and the substrate surface.

In one aspect, the present invention sets forth a method of preparing aself-release substrate as otherwise described herein, the methodincluding: combining a polyhedral oligomeric silsesquioxane with athermoplastic to make a mixture; applying the mixture to a substratesurface; and drying the applied mixture on the substrate surface.

In a more specific aspect, the polyhedral oligomeric silsesquioxane is afluorous polyhedral oligomeric silsesquioxane. In a more specificaspect, the fluorous polyhedral oligomeric silsesquioxane is a —CF₃terminal fluorous polyhedral oligomeric silsesquioxane.

In one aspect, the present invention sets forth a method as otherwisedescribed herein, the method further including: cleaning the substratesurface before applying the mixture thereto. In a more specific example,cleaning the substrate surface includes applying a surfactant, applyingan alcohol, applying an aromatic solvent, applying a functional organicsolvent, plasma etching, flame exposure, acid etching, or electrical arcexposure.

In one aspect, the present invention sets forth a method as otherwisedescribed herein, wherein applying the mixture includes spraying, dipcoating, web coating, roll coating, electrodeposition, vapor deposition,or implantation.

In one aspect, the present invention sets forth a method of preparing aself-release substrate, the method including: applying at least twolayers that include a polyhedral oligomeric silsesquioxane to asubstrate surface to form a first plurality of oligomeric silsesquioxanelayers; applying a layer comprising at least two layers that include athermoplastic to the substrate surface to form a second plurality ofthermoplastic layers; and

drying the applied layers on the substrate surface.

In a more specific aspect, the polyhedral oligomeric silsesquioxane is afluorous polyhedral oligomeric silsesquioxane. In a more specificaspect, the fluorous polyhedral oligomeric silsesquioxane is a —CF₃terminal fluorous polyhedral oligomeric silsesquioxane.

In a more specific aspect, the first plurality of polyhedral oligomericsilsesquioxane layers is applied before applying the second plurality ofthermoplastic layers. In another more specific aspect, one layer of thesecond plurality is applied after applying each layer of the firstplurality.

In a more specific aspect, the present invention sets forth a method asotherwise described herein, the method further including: drying theapplied layer of the first or second plurality before applying the nextlayer of the second or first plurality.

In a more specific aspect, the present invention sets forth a method asotherwise described herein, the method further including: applying atleast two layer that include an additive to the substrate surface toform a third plurality of additive layers, wherein the additive impartsa surface energy of less than about 15 mJ/m². In a more specific aspect,the additive is a —CF₃ terminal fluorous compound.

In a more specific aspect, the present invention sets forth a method asotherwise described herein, the method further including: cleaning thesubstrate surface before applying any layer of the first, second, orthird plurality thereto.

In a more specific aspect, the present invention sets forth a method asotherwise described herein, wherein cleaning the substrate surfaceincludes applying a surfactant, applying an alcohol, applying anaromatic solvent, applying a functional organic solvent, plasma etching,flame exposure, acid etching, or electrical arc exposure.

In a more specific aspect, the present invention sets forth a method asotherwise described herein, wherein applying the mixture includesspraying, dip coating, web coating, roll coating, electrodeposition,vapor deposition, or implantation.

In one aspect, the present invention sets forth a method of preparing aself-release substrate, the method including: applying at least twolayers that include an additive to a substrate surface to form a firstplurality of additive layers, wherein the additive imparts a surfaceenergy of less than about 15 mJ/m²; applying at least two layers thatinclude a thermoplastic to the substrate surface to form a secondplurality of thermoplastic layers; and drying the applied layers on thesubstrate surface. In a more specific aspect, the additive is a —CF₃terminal fluorous compound.

In one aspect, the present invention sets forth a composition configuredto be applied to a surface of a substrate and to render the surfaceself-release as substantially described herein.

Turning now to the figures, and in particularly, FIG. 1, a flowchart 10illustrating a method of preparing and applying a surface coating isshown and described below in detail. At start, a polyhedral oligomericsilsesquioxane (“POSS”) is selected (Block 12). The POSS may befluorinated (i.e., “F-POSS”) and having a chemical structure 14 as shownin FIG. 2. More particularly, the F-POSS 14 may be octakis(1H,1H,2H,2H-heptadecafluorodecyl) polyhedral oligomeric silsesquioxane(“F-decyl POSS”), wherein each R_(f) group of FIG. 2 represents aheptadecafluorodecyl; however, any fluorinated alkyl group including atleast four perfluorinated aliphatic carbons in a linear sequence andterminating in a trifluoromethyl (—CF₃) group, wherein the terminaltrifluoromethyl group forms a part of the aforementioned linearsequence, may be used. For simplicity, any molecular fragment that meetsthe aforementioned sequential chemical structure requirements will bedescribed herein as a “—CF₃ terminal fluorous” sequence. Furthermore,the R_(f) groups need not all be identical, as long as each and everygroup contains at least one —CF₃ terminal fluorous sequence. To functionproperly in the invention, the F-POSS molecules must be capable ofself-assembly such that a well-ordered array of fluorinated chains formson a surface to which the F-POSS molecules are applied so that amajority of the outermost molecular layer at the surface is formed bythe terminus of a —CF₃ terminal fluorous group.

POSS nanostructures may be synthesized in accordance with U.S. Pat. No.6,716,919, entitled NANOSTRUCTURED CHEMICALS AS ALLOYING AGENTS INPOLYMERS; U.S. Pat. No. 7,897,667, entitled FLUORINATED POSS AS ALLOYINGAGENTS IN NON-FLUORINATED POLYMERS; and U.S. Pat. No. 7,193,015,entitled NANOSTRUCTURED CHEMICALS AS ALLOYING AGENTS IN FLUORINATEDPOLYMERS. The disclosures of these references are incorporated herein byreference, each in its entirety.

In addition to POSS compounds, one or more additives—in one aspect,discrete compounds containing one or more —CF₃ terminal fluorous groupsthat self-assemble to form stable —CF₃ terminal fluorous surfaces—may besubstituted in part or in whole for the POSS compound. Examples of sucha compound include perfluorooctanoic acid, perfluorohexanoic acid,perfluorooctane, and 1H,1H,1H,2H,2H-heptadecafluorodecane. In someembodiments, the molecular weight of the additive will exceed 1000g/mol, to limit the fugacity of the compound and thereby increase thedurability of the surface chemical structure. In some other embodiments,the —CF₃ terminal fluorous surface will be thermodynamically stable attemperatures exceeding 85° C.

Likewise, a thermoplastic is selected (Block 12), which may be, forexample, poly(methyl methacrylate) (“PMMA”). Any other amorphouspolyacrylate, poly(alkyl)acrylate, polystyrene, polyolefin,polyacrylonitrile, polysulfone, polybutadiene, polyethersulfone,poly-D-lactic acid, or any other amorphous thermoplastic not swelledmore than about 10% by water, comprising less than about 20 wt %fluorine, and comprising less than about 5 wt % of groups impartingwater solubility (such as alcohol, carboxylic acid, or ionomeric groups)may be used. An important limitation is that the thermoplastic's glasstransition temperature must be at least 20° C. higher than the intendeduse temperature, e.g., at least 30° C. higher than the intended usetemperature. If the glass transition temperature does not meet theserequirements, then large crystals of an F-POSS, a fluorinatedanti-adhesion agent, or both will grow on the surface, leading topinning defects and increased surface roughness. The selection of thethermoplastic is motivated by the need for the —CF₃ terminal fluoroussurface to self-assemble. Too much fluorine in the thermoplastic willlead to an insufficient thermodynamic driving force to segregate thefluorous groups at the surface. Crystallinity or cross-linking willinhibit the segregation process. Too much ingress of water will resultin thermodynamic driving forces that push the fluorous groups away fromthe surface rather than toward it.

In Block 16, the selected POSS (weight percent ranging from 0.1% to 70%by weight, e.g., 10% to 30% by weight) is mixed with the selectedthermoplastic (weight percent ranging from 30% to 99.9%, e.g., 70% to90%) and dissolved in a suitable solvent at concentrations ranging from0.01 mg/L to 200 mg/L, e.g., 1 mg/L to 50 mg/L; 10 mg/L to 30 mg/L. Thesuitable solvent is selected, at least in part, to be compatible with aselected method of treating a substrate with the mixture, which isdescribed in great detail below. Generally speaking, the suitablesolvent is a semi-fluorinated hydrocarbon, semi-fluorinated hydrocarbonether, perfluorinated hydrocarbon, or perfluorinated hydrocarbon ether.Asahiklin AK225G is an example of a suitable solvent.

The range of useful weight percent for the selected F-POSS is determinedmainly by two factors: (i) the possible concentration of fluorinatedgroups at the outermost layer of the surface, and (ii) their rate ofmigration to the outer layer (rather than crystallization). At very lowweight percentages, from 0.1% to as much as 10%, there may be aninsufficient quantity of silsesquioxane present to permit accumulationof a complete and continuous coverage of fluorinated groups at theoutermost molecular layer of the surface. At very high percentages, fromas little as 30 wt %, the silsesquioxane may crystallize rapidly withinthe mixture of silsesquioxane, thermoplastic, and solvent during theprocess of forming the dried coating. Rapid crystallization willimmobilize the silsesquioxane, thereby preventing migration to theoutermost molecular layer at the surface.

The range of useful weight percent for F-POSS may also be influenced bythe amount of other fluorous compounds present (e.g., other F-POSS oradditives). In some embodiments, the F-POSS concentration may apply tothe total concentration of all F-POSS components of a mixture; allF-POSS and fluorous additives as set forth herein; or all —CF₃ terminalfluorous species.

Any given substrate may be treated or coated with the mixture of Block16, and may include, for example, substrates comprising a metal, aplastic, a ceramic, and composites thereof. Substrates may alternativelyinclude non-volatile liquid substrates, such as heavy oils or ionicliquids.

Before the mixture is applied to a given substrate, a surface of thesubstrate that will receive the mixture application may optionally becleaned, pretreated, or both, so as to remove surface contaminants,control the surface topography, control the chemical composition of thesurface, to facilitate the treatment or coating process, or acombination thereof (Optional Block 18). Cleaning may include treatmentwith surfactants, alcohols, aromatic solvents (e.g., toluene orxylenes), functional organic solvents (e.g., acetone or ethyl acetate),plasma etching, flame exposure, acid etching, or exposure to electricalarcs. The optional pretreatments, according to some embodiments of thepresent invention, may include applying a primer layer configured topromote adhesion of the mixture to the substrate. Other pre-treatmentsmay also be applied to prevent corrosion, remove contaminants, altersurface texture, impart color or other tracing and trackingcapabilities, or otherwise improve overall performance of the system.

With the mixture prepared (Block 16) and the optional cleaning and/orpretreatment (Block 18) complete, the mixture may be applied to thesurface of the substrate using one of a plurality of coating ortreatment processes (Block 20). Exemplary coating or treatment processesinclude, but are not limited to, spraying, dip coating, web coating,roll coating, electrodeposition, vapor deposition, implantation, orcombinations of one or more thereof. As alluded to previously, thecoating or treatment process will at least partially dictatecharacteristics of the solvent used in preparing the mixture. Forinstance, the solvent(s) may be selected so as to achieve more than99.9% evaporation within the drying period (e.g., a span of a fewseconds to a few hours) upon exposing the coated substrate to processtemperatures that are compatible with maintaining the integrity of thesubstrate or the processing environment. Also, for instance, theconcentration of solid ingredients in the coating process may be tunedto provide desired rheological characteristics, such as a viscosity lowenough to allow for uniform distribution of the treatment or coating buthigh enough to prevent excess dripping on standing. These considerationsare widely known to those skilled in the art of formulating and applyingsurface treatments and coatings.

The treatment or coating ingredients may be applied in a single step(e.g., a simple embodiment of FIG. 1 Path A's Block 20), or they may beapplied in a sequence of application and drying steps (e.g., anembodiment of FIG. 1 Path B's Blocks 20 and 22) that is optionallyrepeated. The compositions of the treatments or coatings applied inthese repeated steps may remain the same, or they may vary from cycle tocycle. The treatment or coating ingredients may also be applied inratios that vary over time within a single cycle so as to producespatial gradients in the applied coating. The treatment or coatingingredients may also include reinforcing particles, toughness enhancingparticles, additives to control rheology, pigments and dyes, tracing andtracking indicators, indicators for aiding in measurement of coatingproperties, additives to improve abrasion and wear characteristics, orother additives and modifiers needed to improve one or more aspects oftreatment or coating performance unrelated to fouling release, butcommonly required in treatment or coating products, as readilyunderstood by skilled practitioners of the art of treatment or coatingformulation.

In any event, and with the coating or treatment complete, the substratewith the coating or treatment thereon may be dried. Optionally, and asprovided in Block 22, the coating or treatment on the surface of thesubstrate may be dried via a heat treatment, in vacuum, by applicationof forced convection, by desiccation, or any other method suitable forremoving solvents in times ranging from a few seconds to a few hours.The drying process may consist of a single step, or of multiple steps insequence, possibly nested within repeating cycles of application anddrying, as previously disclosed.

If no drying step is used, the coating must remain quiescent for acuring period ranging from at least 10 milliseconds to as long as 400hours, which depends on variables (e.g., coating thickness and ambienttemperature) that are understood by those skilled in the art. Thequiescent period may also be accomplished during one or more dryingsteps. The quiescent period is required in order to allow for thephysical rearrangement of molecules within the coating, as well asformation of the proper homogeneity and topography of the surface. Aspreviously noted, the physical rearrangement of the molecules into theproper form is critical to the function of the invention, as is theformation of the correct topology and the homogeneity of the surface.

After drying, the topography of the dried surface may be furthermodified by methods such as abrasion, re-exposure to solvent followed byre-drying, or rubbing. These methods for topographical surfacemodification are well-known to those skilled in the art. To minimize theadhesion of fouling, the topographical roughness features of the surfaceare kept to a minimum. In embodiments, the average roughness (R_(a)) ofthe surface over an area of 0.1 mm×0.1 mm does not exceed 1 μm. In someembodiments, R_(a) over an area of 0.1 mm×0.1 mm does not exceed 200 nm(e.g., about 200, 175, 150, 125, 100, 80, 60, 50, 40, 30, or 20 nm). Insome embodiments, R_(a) over an area of 0.1 mm×0.1 mm does not exceed 20nm (e.g., about 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6,5, 4, 3, 2, or 1 nm). To minimize the interference with heat transfer,the average thickness of the deposited, dried, and modified treatment orcoating does not exceed 1 μm (e.g., about 1000, 950, 900, 850, 800, 750,700, 650, 600, 550, 500, 450, 400, 350, 300, 250, or 200 nm). In someembodiments, the average thickness does not exceed 100 nm (e.g., about100, 90, 80, 70, 60, 50, 40, 30, or 20 nm).

With reference now to FIG. 3A, removal of a mineral scale 26 from asubstrate 28 treated or coated in accordance with an embodiment hereinis shown. Substrate 28 is illustrated here as an outer surface (e.g., ofa section of tubing) 30 in contact with a fluid (not shown). At start, aturbulent fluid flow 32 is generated (for example, from a water nozzle34) and is directed toward an interface 36 between the mineral scale 26and the coated or treated surface of the substrate 28. The fluidsupplying the turbulent fluid flow 32 may include, but is not limitedto, water, another solvent (e.g., methanol or acetone), a detergent(e.g., sodium dodecyl sulfate), a petroleum fraction (e.g., kerosene),or combinations thereof, wherein each fluid may be a liquid or a gas.The fluid may consist of multiple phases in contact, such as a petroleumphase (e.g., kerosene) mixed with an aqueous phase (e.g., salt water,sea water, or an aqueous solution of a salt). According to still anotherembodiment of the present invention, particulates (not shown) may besuspended within the fluid, such particulates comprising, for example,sand grains. If desired, the fluid may also be heated, such as by heattransfer from the interior of the substrate 28. The treated or coatedsubstrate 28 may be wholly immersed in one or more fluid phases, withtreatment or coating present on the outer surface only, or the treatedor coated substrate may partially or wholly enclose one or more fluidphases, with the inner surface treated or coated, or both inner andouter surfaces may be exposed to one or more separate or continuousfluid phases, with either or both of the inner and outer surfacestreated or coated (with the same or different treatments or coatings).

When the laminar or turbulent fluid flow 32 reaches or exceeds acritical threshold, as determined by the particular geometricconfiguration of the coated or treated surface 30 and surrounding flow,if any, the fluid velocity provides a lifting force over the surface 30,which is created by a Venturi effect. The result is a shear force on anoutermost solid layer of substrate 28. In some embodiments of thepresent invention, transient radial and tangential forces may beassociated with fluctuations in the fluid velocity field. If present,particulates suspended within the turbulent fluid flow 32 may furtherprovide an impact force. In toto, the forces are transmitted to thecoated or treated substrate 28, thereby creating stresses at theinterface 36. Such stresses, particularly at interfacial flaws at theinterface 36 between the coated or treated surface 30 and the mineralscale 26 are intensified, which causes local delamination of the mineralscale 26 to yield a delaminated portion 38 of the surface 30 of thesubstrate 28. With further exposure to the turbulent fluid flow, thesize of the interfacial flaws, and thereby the delaminated portion 38,propagate across the interface 36.

Moreover, according to some embodiments of the present invention,exposure to the turbulent fluid flow 32 may generate vibrations orpressure fluctuations, which further facilitate delamination by aself-release process.

Coating or treatment of the surface of a substrate, as taught in thevarious embodiments herein, should not be limited to outer substratesurfaces as exemplified in FIG. 3A. According to another exemplaryembodiment of the present invention illustrated in FIG. 3B, a lumen 40extending the longitudinal axis 42 of a tube 44 is coated or treatedaccording to an embodiment of the present invention. An outer surface 46of the tube 44 remains untreated.

In contrast, FIG. 3C illustrates a similar tube 48 with a lumen 50 alongits longitudinal axis 52 and an untreated outer surface 54, but withoutcoating or treatment. FIG. 3C also shows the long-term effects ofexposing the lumen 50 to so-called “tap” water. Over time, as suggestedabove in the Background of the Invention, mineral scaling 56 may depositonto at least a portion of the untreated lumen 50 of the tube 54 of FIG.3C.

The treated lumen 40 of the tube 44 of FIG. 3B would resist such mineralscale deposition. Assuming, arguendo, mineral scale were to deposit onthe lumen 40 of the tube 44 of FIG. 3B, turbulent fluid flow, generallyalong the longitudinal axis 42 and in the manner described above forFIG. 3A, would promote delamination. In some embodiments where tap watercontinuously and turbulently flows through the tubing 44 of FIG. 3B, asteady state condition may be achieved whereby mineral scale depositionslike 56 (FIG. 3C) are delaminated within a short period of time, if notnearly instantaneously, after formation or deposition.

The following examples illustrate particular properties and advantagesof some of the embodiments of the present invention. Furthermore, theseare examples of reduction to practice of the present invention andconfirmation that the principles described in the present invention aretherefore valid but should not be construed as in any way limiting thescope of the invention.

Example 1

Outer surfaces of welded and annealed type 316/316L stainless steeltubes, each measuring 560 mm in length (22 inches), 6.35 mm outerdiameter (0.250 inches), and 4.57 mm inner diameter (0.180 inches),purchased from Associated Tube Canada (Markham, Ontario, Canada) via PacStainless Ltd. (Seattle, Wash.) and were in accordance with ASTMA-249/10, ASTM A-269/10, AMSE SA 249 2007, and BRS 7, were processed asfollows:

The outer surface of each tube was prepared by washing with liberalamounts of acetone and rinsed with isopropanol. Each tube was thenpassed slowly through a propane flame, which removed any residualorganic compounds. Each tube was then left to cool to room temperature.

Solid ingredients (described below) for coating or treatment weredissolved in Asahiklin AK225G. The ingredients were weighed,individually, mixed together in a container to which the AsahilkinAK225G was added. Ingredients were allowed to dissolve while stirringusing a magnetic stir bar. A 20-mL aliquot of the solution (having afinal solid content of 30

$\left. \frac{mg}{mL} \right)$

was transferred into a Polytetrafluoroethylene (“PTFE”) lined bottleattached to a Paasche VL0610 double action siphon feed airbrush (PaascheAirbrush Co., Chicago, Ill.). The airbrush was driven by an air-linewith a regulator set to approximately 25 PSI. The tip, needle, andaircap used were model numbers VLT-1, VLN-1, and VLA-1, respectively(Paasche Airbrush Co.). Each aliquot was applied to one tube, in asweeping motion, from end-to-end, while rotating the tube about itslongitudinal axis to ensure full coverage. A consistent spray patternwas maintained by locking the line adjustment assembly to withdraw thepin of the airbrush to a fixed distance, and the airbrush was fixed at adistance of about 150 mm (5.9 inches) from the tube being coated.Samples were then left to dry under ambient conditions for a period oftime, ranging from about 5 min to about 60 min. Drying was typicallyachieved in 5 min, however, for operational convenience, samples wereleft out for as long as 60 min.

As shown in FIG. 4, a total of three tubes were prepared. A first tube,designated as a “white” tube (and illustrated herein as “W”), wasprepared as described above, but with no solid ingredients or liquidingredients other than Asahiklin AK225G. A second tube, designated the“blue” tube (and illustrated herein as “B”), was prepared as describedabove, but using only octakis(1H,1H,2H,2H-nonafluorohexyl) polyhedraloligomeric silsesquioxane (F-hexyl-8-T8 POSS, with each R_(f) groupbeing 1H, 1H,2H,2H-nonafluorohexyl) and Asahiklin AK225G as theingredients. A third tube, designated the “red” tube (and illustratedherein as “R”), was prepared by applying a layer of Pro-Gray Primer 7582(Rust-Oleum Corp, Vernon Hills, Ill.) to the third tube (directly fromthe manufacturers spay can), dried (per manufacturer directions), andthen treated or coated with the solution having F-hexyl-8-T8 POSS as theingredient (thus, similar to the B tube). Measurements indicated that athickness of the Pro-Gray Primer was approximately 0.065 mm (0.0026inches).

Each of the three tubes W, B, and R was mounted in a separatesingle-tube, tube-and-shell heat exchanger (70, 72, and 74,respectively). The heat exchangers were connected to a single watersource 76. The shells of each heat exchanger (70, 72, 74) were made oftransparent acrylic polymer to enable visual inspection and photographyduring testing. The test was conducted over a period of 46 hours and 5minutes. During the test, 100 gallons of cold water were circulated bypump 96 between the outer surface of each tube (84, 86, 88) and theinner surface of each shell (78, 80, 82). The cold water was collected,without further treatment, from a municipal well within thePittsburgh-Bodega, Calif. water district. The cold water was maintainedat an average temperature of 70.8° F. and circulated at an average flowrate of about 6.54 gallons per minute (about 2.8 linear feet persecond). Analysis of the cold water showed an initial pH of 8.03,electrical conductivity of 1711

$\frac{\mu \; S}{cm},$

total dissolved solids at 1222 ppm, salinity at 1222 ppm, and calciumcarbonate concentration at 420 ppm. The oil content of the cold waterwas negligibly small. The calcium carbonate concentration measured on asample of the cold water approximately one day after start of the testwas 440 ppm in a first measurement and 450 ppm in a second measurement.At conclusion, the cold water showed a pH of 8.18, electricalconductivity of 1614

$\frac{\mu \; S}{cm},$

total dissolved solids of 1148 ppm, salinity of 1149 ppm, and calciumcarbonate concentration of 370 ppm. The changes observed of the coldwater from the start of testing to the end of testing are consistentwith deposition of calcium carbonate (primarily) and, to a lesserextent, deposition of other minerals on the surfaces of the tubes.

While testing, distilled water (source 98) was heated in heater 100(average temperature of 127.7° F.) and circulated through the interiorof the three tubes (W, B, R) by pump 102 at a flow rate of 0.30 gallonsper minute. Final weights of the tubes at completion of the testing areprovided below in Table 1. Gross weight gains were similar for all threetubes and, on a per area basis, the weight gain was higher for thecoated and/or treated second and third tubes (B and R, respectively) incontrast to the first tube (W) treated only with olvent. Despite thepresence of the F-decyl POSS treatment, no significant reduction inweight gain was realized, which, at least facially, appears to beinconsistent with the expectations implied by the teachings of U.S.Application Publication No. 2013/0122225, entitled ARTICLES AND METHODSPROVIDING SCALE-PHOBIC SURFACES. While wishing to not be bound by anyparticular theory, in this case where the test environment may moreaccurately represent real world conditions with more nucleation events(as compared to a controlled laboratory environment), the effectsobserved in this study are consistent.

TABLE 1         Tube Sample       Final Weight (g) $\quad\begin{matrix}{{Weight}\mspace{14mu} {Gain}} \\{{per}\mspace{14mu} {Area}} \\\left( \frac{g}{{cm}^{2}} \right)\end{matrix}$   Adhered thickness of mineral scale (mm) 1^(st) Tube (W)67.656  0.0321 0.070 2^(nd) Tube (B) 60.3514 0.0218 0.085 3^(rd) Tube(R) 67.6572 0.0297 0.075

After completion of the test and subsequent drying of the three tubesunder ambient conditions, the tubes were shipped to an analysis facilitywhere the thickness of adhered mineral scale at multiple points alongeach tube was measured using digital calipers. Resultant values areprovided in Table 1, above. These results indicate that while themineral scale may have formed with a higher density on the second (B)and third (R) tubes, there was not a significantly large reduction inthe amount of mineral scale adhered achieved by the F-decyl POSStreatments.

Additional evaluation of the tubes after testing was conducted with atape test adapted from AMERICAN SOCIETY FOR TESTING AND MATERIALS,“Method A,” D3359-97 Measuring Adhesion by Tape Test. More particularly,and with reference to FIG. 5, the specific test procedure includedmeasuring an internal diameter, d₁, of a bare portion 104 (that is, thearea without mineral scale) of each stainless steel tube (W, B, R) usingdigital calipers in three locations and average recorded. A seconddiameter, d₂, of a section covered with mineral scale 106 was thenmeasured for each tube (W, B, R) in three locations and averagerecorded. Two marks (one of the two is illustrated as “X”) wereinscribed on each tube 60, wherein each mark X is about 6 mm² and spacedaway from the other mark (not shown) of the same tube (W, B, R) by adistance ranging from about 10 mm to about 20 mm. A first length of tape(not shown; Scotch® brand transparent tape by 3M Global Gateway, St.Paul, Minn.) is pulled to expose fresh adhesive from the reel anddisposed. A second length of tape 108 is then pulled in the same mannerand applied to the tube (W, B, R), over one of the two marks X and suchthat the tape 108 is centered over the mark X. The second length of tape108 is pressed and smoothed on and around an area of the tube (W, B, R)over and proximate to the mark X. The second length of tape 108 is thenremoved by pulling with a quick movement in the direction of the arrow110 and along the lengthwise central axis 112 of the mark X. The pullingangles are preferably close to 180°. While looking at the adhesive sideof the tape, the amount of mineral scale deposit removed is evaluatedaccording to Table 2, below. The process was repeated for both marks oneach tube (W, B, R). Results are provided below in Table 3.

TABLE 2 Rating Description 0 Removal beyond the area of the X 1 Removalfrom most of the area of the X under the tape 2 Jagged removal alongmost of incisions on either side 3 Minor, jagged removal along incisionson either side 4 Trace peeling or removal along incisions or at theirintersection 5 No peeling or removal

TABLE 3 Tube Sample First Pull Second Pull 1st Tube (W) 3 3 2nd Tube (B)0 0 3rd Tube (R) 4 2

The mineral scale of the second tube (B), having only the F-decyl POSStreatment, was easily removed by the tape 108. In fact, the mineralscale of the second tube (B) delaminated with ordinary handling. Themineral scale of the first and third tubes (W, R) adhered fairly well.The difference in adhesion indicated that, at least for the unprimedsecond tube (B), the F-decyl POSS treatment remained present throughoutand after the test. The surface energy of the F-decyl POSS layer usedhas been reported as 11.6

$\frac{mJ}{m^{2}}$

according to the Girifalco-Good method taught in Chhatre et al.,“Fluoroalkylated Silicon-Containing Surfaces-Estimate of Solid SurfaceEnergy,” ACS Appl. Matl. Interfaces, Vol. 2 (2010) 3544-3554. However,the results did not indicate a significant decrease in observed mineralscale accumulation or self-release properties. Moreover, as the data forthe third tube (R) indicate, simple deposition of a low surface-energymaterial, such as F-decyl POSS, did not result in a treated surface withlow adhesion. Again, without wishing to be bound by a particular theory,the heterogeneous and swellable nature of the primer layer is likely tohave resulted in a heterogeneous distribution of F-decyl POSS on thesurface, with some penetration of the primer by F-decyl POSS. The resultis a broad distribution of surface energy characteristics. Under suchconditions, the adhesion of mineral scale was not altered significantly.

Example 2

Three stainless steel tubes, from the same production lot as those ofExample 1, were also coated or treated in the manner described inExample 1. A first tube (W) was treated with a solution having no solidingredients or liquid ingredients, other than Asahiklin AK225G (similarto the first tube (W) of in Example 1). A second tube (B) was treatedwith a solution comprising a 4-to-1 weight ratio of poly(methylmethacrylate) (Part No. 182230-1KG, 9011-14-7, Sigma Aldrich Corp., St.Louis, Mo., having a molecular weight of about 120000, and T_(g) of99.0° C.) (“PMMA”) to F-decyl POSS and no liquid ingredients other thanAsahiklin AK225G. A third tube (R) was treated with a solutioncomprising a 7-to-3 weight ratio of PMMA to F-decyl POSS and no liquidingredients other than Asahiklin AK225G.

As in the apparatus of FIG. 4, all three tubes (W, B, R) were mounted inseparate single-tube tube-and-shell heat exchangers (70, 72, 74), whichwere connected to a single water source 76. The shell (78, 80, 82) oneach heat exchanger (70, 72, 74) was made of transparent acrylic polymerto allow for visual inspection and photography during the test. The testwas conducted over a period of 116 hours and 42 minutes. During thetest, 100 gallons (25 gallons of which were freshly supplied) of coldwater from water source 76 were circulated between the outer surface(84, 86, 88) of each tube (W, B, R) and the inner surface (90, 92, 94)of each shell (78, 80, 82). The cold water was collected, withoutfurther treatment, from a municipal well within the Pittsburgh-Bodega,Calif. water district. The cold water was maintained at an averagetemperature of 66.8° F. and circulated at an average flow rate of 6.41gallons per minute (about 2.7 linear feet per second). The range of coldwater flow rates recorded over the duration of the test extended from5.93 gallons per minute to 6.94 gallons per minute. Analysis of the coldwater showed an initial pH of 8.06, electrical conductivity of 1644

$\frac{\mu \; S}{cm},$

total dissolved solids at 1172 ppm, salinity at 1172 ppm, and calciumcarbonate concentration at 450 ppm. The oil content of the cold waterwas negligibly small. At conclusion, the cold water showed a pH of 8.27,electrical conductivity of 1660

$\frac{\mu \; S}{cm},$

total dissolved solids of 1181 ppm, salinity of 1184 ppm, and calciumcarbonate concentration of 410 ppm.

While testing, distilled water from water source 98 was heated by heater100 to an average temperature of 128.4° F. and was circulated by pump102 through the interior of the tubes (W, B, R) at a flow rate of 0.30gallons per minute. Final weights of the tubes (W, B, R) at completionof the testing are provided below in Table 4. During testing, the thirdtube (R) demonstrated self-release of the mineral scale layer (FIG. 6).The second tube (B) demonstrated self-release, but to a lesser extentthan the third tube (R). The first tube (W) did not exhibit self-release(FIG. 7)

TABLE 4         Tube Sample       Final Weight (g) $\quad\begin{matrix}{{Weight}\mspace{14mu} {Gain}} \\{{per}\mspace{14mu} {Area}} \\\left( \frac{g}{{cm}^{2}} \right)\end{matrix}$   Adhered thickness of mineral scale (mm) 1^(st) Tube (W)66.7654 0.0114 0.020 2^(nd) Tube (B) 66.7182 0.0092 0.010 3^(rd) Tube(R) 59.4175 0.0066 0.000

After completion of the test and subsequent drying of the tubes (W, B,R) under ambient conditions, the tubes were shipped to an analysisfacility. As shown in FIG. 8, the second tube (B) had almost no mineralscale left on its surface, the third tube (R) had only a small amount ofmineral scale adhering thereto, and the first tube (W) had an intactlayer of mineral scale. Adhesion testing of the mineral scale wasperformed as described above in Example 1. Both the second and thirdtubes (B, R) returned a value of “0” while the first tube returned avalue of “5.”

The thickness of mineral scale deposited on the first tube (W) was 0.02mm. The mineral scale deposit on the third tube (R) had a thickness of0.01 mm. The second tube (B) had insufficient mineral scale remaining toestimate a thickness.

Example 3

The following example illustrates the self-assembly of a fluorinatedsilsesquioxane contained in a thermoplastic matrix, and the influence ofthe self-assembly process on contact angle characteristics of a surface.In accordance with the teaching of Meuler (supra), the receding contactangle indicates the strength of adhesion of a solid substrate to thesurface. Because the solid in question is a hydrated salt solution, thebest common liquid probe used to indicate the likely adhesion strengthis water. (The temperatures required of a molten salt probe liquid arenot practical for analysis of the surfaces in question.)

Using octakis(1H,1H,2H,2H-heptadecafluorodecyl)silsesquioxane as theanti-adhesive agent, poly(methyl methacrylate) as the matrixthermoplastic, Asahiklin AK225G as the solvent, and a ratio of 20:80 ofanti-adhesive agent to thermoplastic, surfaces were prepared by spincoating the aforementioned solution (30 mg/mL total solids content) ontoclean silicon wafers. The geometric characteristics of the surfaces wereanalyzed using a surface interferometer (Vecco Instruments, Inc.,Plainwell, N.Y.) to obtain topographical maps of regions on the surface,as presented in FIG. 9. A Rame-Hart goniometer was then used to collectadvancing and receding contact angle characteristics of the surfaces,using pure water as a probe liquid, with the results shown below inTable 5. The same surfaces were then heated for 1 hour at a temperatureof 90° C., about 10° C. below the glass transition temperature of thethermoplastic matrix. At 90° C., the thermoplastic matrix allows for arapid annealing of the surface texture. As indicated in FIG. 9 (upperpanel), the surface prior to heating at 90° C. is extremely smooth(having an average roughness, R_(q), below 1 nm) and generallyfeatureless, exhibiting only some modest curvature and undulation overlength scales of tens of microns. This result indicates that theroughness of the surface may be made smaller than 1 nm using the coatingcompositions and procedures specified in the invention. In otherexamples, the roughness of the surface may be adjusted between 1 nm andabout 1 μm by changing variables such as the drying time andtemperature, as understood by one skilled in the art.

In contrast, the surface after heat treatment (FIG. 9, lower panel)exhibits a texture dominated by well-formed crystalline domains of thefluorinated silsesquioxane. At the boundaries of these domains(indicated by the bright lines in FIG. 9, lower panel), the surfacecontains nanoscale crevice-like features. Within these crevices, thethermoplastic matrix exhibits a low level of fluorinated silsesquioxane,and therefore lacks anti-adhesive properties. As a result, thesefeatures serve as surface defects where solids and liquids can becomepinned to the surface. The effect is manifest in the contact angle datashown below in Table 5. The defects created by the heat treatmentprocess lower the receding contact angle and are therefore likely toincrease the adhesion of mineral scale. To avoid the formation of suchdefects, the skilled artisan must select a matrix thermoplastic with aglass transition temperature at least 20° C., and preferably at least30° C., above the intended use temperature.

TABLE 5 Advancing Receding Contact Uncer- Contact Uncer- Angle taintyAngle tainty R_(q) (degrees) (degrees) (degrees) (degrees) (nm) No heattreatment 117 0.20 104 0.40 118 0.24 107 0.40 Average 118 0.31 106 0.570.77 With heat 115 0.24 88 1.00 treatment 117 0.27 95 0.72 Average 1160.36 91 1.23 1.66

Example 4

The following example illustrates that the physical characteristics ofthe thermoplastic matrix, as controlled by factors such as the coatingdeposition process, influence the self-assembly of a fluorinatedsilsesquioxane in such a way as to affect the adhesion of solid objectsto a surface of a coating comprising the thermoplastic matrix and thesilsesquioxane.

Using octakis(1H,1H,2H,2H-heptadecafluorodecyl)silsesquioxane as theanti-adhesive agent, poly(methyl methacrylate) as the matrixthermoplastic, Asahiklin AK225G as the solvent, and a ratio of 20:80 ofanti-adhesive agent to thermoplastic, surfaces were prepared by dipcoating stainless steel tubes in the aforementioned solutions (30 mg/mLtotal solids loading). By adjusting the speed of tube withdrawal fromthe dip coating process, coating with differing roughness values wereobtained. The roughness of the coatings was quantified using a surfaceinterferometer (Veeco Instruments, Inc., Plainwell, N.Y.), using theparameter R_(q) as the quantitative roughness indicator. Advancing andreceding contact angles were then measured using a Rame-Hart goniometerand pure water as the probe liquid. FIG. 10 shows a plot of theadvancing and receding contact angles as a function of the roughnessparameter R_(q). In particular, the receding contact angle decreasesmarkedly as the roughness increases. Such behavior is a well-knowncharacteristic of the fully-wetted state of rough surfaces. Because thereceding contact angle indicates the relative adhesion strength ofhydrated salts to the surface, FIG. 10 indicates that the adhesionstrength will decrease as the roughness of the surface is decreased. Toobtain self-release of adhered mineral deposits, the surface roughnessmust therefore be maintained below a critical value. The particularcritical value depends on the magnitude of the forces generated by thefluid flow and the nature of the mineral scale, as understood by thoseskilled in the art.

Example 5

The following example illustrates that not all fluorine containingsubstances that form a coating on a surface, and in particular notperfluorinated substances that have previously been identified asreducing the extent of mineral scale deposit on a surface, are suitablefor the present invention. As previously mentioned, the receding contactangle of the surface in contact with pure water serves as a reliableindicator of the relative strength of adhesion of hydrated mineralscale. Table 6 lists the receding contact angles in contact with purewater of surfaces prepared by dip coating stainless steel 316 tubes insolutions containing fluorinated substances. In particular, severalgrades of the commercial product Fluorolink, including Fluorolink S10,were used as described in U.S. Pat. App. Pub. No. 2013/1260156. Thereceding contact angles of these coatings were measured using aRame-Hart goniometer.

According to Table 6, the receding contact angles of the Fluorolinkproducts were very substantially lower than those of an appropriatelyselected fluorinated silsesquioxane compound within an appropriatelyselected thermoplastic matrix. From this, it follows that the adhesionof mineral fouling will likely be significantly higher for surfacescomposed of perfluorinated compounds such as Fluorolink S10, as comparedwith the terminal fluorous surfaces of the present invention.

TABLE 6 CA_(adv) stdev CA_(rec) stdev hist stdev Fluorolink P54 107.51.44 0.0 0.00 107.5 1.44 Fluorolink S10 107.5 0.27 63.0 0.61 44.5 0.66FD- 121.0 0.50 94.0 0.43 27.0 0.66 POSS:PMMA

Example 6

This example illustrates that the self-release phenomenon depends on thelevel of shear forces applied to a surface. For embodiments of thepresent invention, there will be a critical threshold value of shearforces above which self-release will take place. This level depends onthe surface composition, state of physical assembly of the molecules atthe surface, surface topography, and surface homogeneity.

In FIG. 11, multiple examples are shown of surfaces comprising a mixtureof octakis(1H,1H,2H,2H-heptadecafluorodecyl) silsesquioxane, andpoly(methyl methacrylate), deposited from Asahiklin AK225G solvent viadip coating of stainless steel tubes and exposed to hard watersolutions. Specifically, the tubes having the B and R labels (i.e.,other than W) contain such surfaces, while the tube having the whitetape label is a control sample having only the stainless steel substrateafter dip coating in solvent only. The experiments were carried out withthe procedures as described in Examples 1 and 2. Within the experimentalapparatus, there exist differing levels of shear forces present on thesurfaces. In particular, there are localized areas near the ends of thecoated tubes where redirection of the fluid flow takes place. Suchredirection of flow creates a localized zone of high shear forces actingon the surface of the tube. Because the surfaces of the presentinvention require a critical threshold value of shear force to producedelamination, it is possible to observe cases where only in thelocalized regions of flow redirection are the shear forces sufficient tocause self-release. Such a phenomenon constitutes an importantexperimental verification of the mechanism of self-release, namely, thatself-release is not associated with defects in the coating (which wouldproduce random locations of self-release). Moreover, self-release is notcaused by any features of the apparatus itself (such as a cold spot),because mineral scale does form on the control sample not having thesurface of the present invention.

As described herein, embodiments of the present invention are directedto a self-release coating or treatment consisting of a thermoplastic anda fluorinated polyhedral oligomeric silsesquioxane. Exemplary datademonstrate that substrates treated or coated in accordance withembodiments of the present invention have decreased weight and decreasedthickness of mineral scale as compared to similar substrates lacking thecoating or treatment.

While the present invention has been illustrated by a description of oneor more embodiments thereof and while these embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus andmethod, and illustrative examples shown and described. Accordingly,departures may be made from such details without departing from thescope of the general inventive concept.

What is claimed is:
 1. A method of preparing a self-release substrate,the method comprising: combining a polyhedral oligomeric silsesquioxanewith an amorphous thermoplastic to make a mixture, wherein thepolyhedral oligomeric silsesquioxane is a —CF₃ terminal fluorouspolyhedral oligomeric silsesquioxane; and applying a first layer of themixture to a surface of a substrate.
 2. The method of claim 1, furthercomprising: applying a second layer of the mixture to the surface of thesubstrate.
 3. The method of claim 1, further comprising: drying thefirst layer before applying the second layer.
 4. The method of claim 3,wherein after drying the first layer, a ratio of the —CF₃ terminalfluorous polyhedral oligomeric silsesquioxane to the amorphousthermoplastic permit segregation and self-assembly of the —CF₃ terminalfluorous groups and resist crystallization and cross-linking.
 5. Themethod of claim 1, further comprising: applying an additive layer to thesurface of the substrate, wherein the additive layer is configured toimpart a surface energy of less than about 15 mJ/m².
 6. The method ofclaim 5, wherein the additive layer comprises a —CF₃ terminal fluorouscompound.
 7. The method of claim 1, further comprising: cleaning thesurface of the substrate before applying the first layer.
 8. The methodof claim 7, wherein cleaning the surface of the substrate comprises astep selected form the group consisting of applying a surfactant,applying an alcohol, applying an aromatic solvent, applying a functionalorganic solvent, plasma etching, flame exposure, acid etching, andelectrical arc exposure.
 9. The method of claim 1, wherein applying thefirst layer is selected from the group consisting of spraying, dipcoating, web coating, roll coating, electrodeposition, vapor deposition,and implantation.
 10. The method of claim 1, wherein the amorphousthermoplastic comprises less than about 5% (w/w) of groups impartingwater solubility, is not swelled more than about 10% by water, and thatcomprises at most about 20% (w/w) fluorine.
 11. The method of claim 1,wherein a glass transition temperature of the amorphous thermoplastic isat least 20° C. higher than an intended use temperature of theself-release substrate.
 12. The method of claim 1, further comprising:resisting an ingress of water while drying the first layer.